As a control apparatus and method for a lean-burn combustion engine according to the prior art, Japanese Patent Laid-Open No. 206822/1983 discloses a controller wherein a swirl control valve for regulating a swirl intensity of combustion air inside an intake port is provided in order to expand a lean limit, and this swirl control valve is driven by an actuator such as a diaphragm.
However, because the controller and the control method described above use the actuator for driving the swirl control valve, they do not consider the fitting space and the cost. As a result, they constitute an intake system having a complicated structure and requiring a high cost of production.